JNeurosci: Highlights from the March 15 issue

Humans' unique language abilities have been attributed in part to a bundle of fibers that connects different parts of the brain associated with the production and comprehension of language. This connectivity — which is much less pronounced in nonhuman primates — is thought to support the working memory needed to learn new words. In a new study, researchers used computer modelling to compare the connectivity between these language areas in monkeys and humans and tested the response of these networks to simulated word learning. The researchers found evidence of verbal working memory only in the human network, in which short connections between nonadjacent language areas of the brain provide information-retention and processing-speed advantages over the "smaller and functionally sluggish" monkey network. These findings could help to explain why monkeys have only been able to achieve a fraction of human vocabulary, even after extensive training.

For as many as a third of migraine patients, the painful headache can be preceded by vision disturbances such as blurriness or sensitivity to light. This migraine aura is the result of altered neural activity called cortical spreading depression (CSD), a phenomenon that could negatively impact brain health over time. In a new study in mice, researchers found that CSD dramatically delays and slows the flow of cellular waste from the brain. Similar impairment of the brain's waste clearance system has been associated with lack of sleep and traumatic brain injury, which are also risk factors for neurodegenerative diseases such as Alzheimer's. Together, these findings raise the possibility that migraine aura could facilitate degenerative processes in the brain.

Obsessive-compulsive disorder (OCD) and Tourette syndrome (TS) are characterized by highly ritualized behaviors that disrupt an individual's daily life. These disorders often occur together and may share a common basis in the brain. In a new study in mice, scientists show that selective elimination of striatal cholinergic interneurons (SCIN) — which were previously found to be impoverished in brain samples of deceased TS patients — leads to altered social interactions that resemble those of OCD and TS patients. It did not affect motor function, balance or locomotion, but resulted in a highly repetitive and structured pattern of social investigations of other mice. This suggests a role for SCIN in regulating social behaviors that become dysfunctional in neuropsychiatric disorders.